As a process for synthesizing 4-methylenepiperidine, there have been known the method wherein an aqueous solution of 4-bromoquinuclidine is heated (P. Brenneisen et al., Helv. Chim. Acta, 48(1), 146-156(1965)) and the method wherein N-benzyl-4-piperidone is reacted with a Wittig reagent and then debenzylation is carried out to obtain 4-methylenepiperidine (M. Mimura et al., Chem. Pharm. Bull., 41(11), 1971-1986(1993)). However, by either of these methods, it is difficult to manufacture a large amount of 4-methylenepiperidine at low cost because of the difficulty of obtaining the starting material or the use of an expensive reagent such as the Wittig reagent.
The object of the present invention is to provide a process for preparing 4-methylenepiperidine efficiently in short process from a cheap starting material which is obtainable at large amount.